I've not opened up this servo before BUT every servo I have opened up will have the pot centered in line with the length of the case(longer portion) so try this.

The pot should have two flat spots on it for turning the main gear... put it the so the lenght is centered with the servo body, now look at you're main gear... if there is a pin or other form of protrusion that would hit stops molded in the upper part of the servo case make sure the pin/lip what ever it is, is also in line with the pot and length of the servo case.

By doing the above you should be back in business